This short story is a prequel to the first Hitchhiker's novel and is a story about Zaphod Beeblebrox, the man with the odd, or rather even, number of heads.
It's a very brief story and nothing much of interest happens at all. It is a bit intriguing that since this is a prequel about Zaphod it means that it takes place before he blocked off sections of his mind, so I suppose it's nice to see what he was like before he became what we know him to be in the main series. Plus there's some nice references to events that take place later on.
Many people who read this in The Ultimate Hitchhiker's Guide to the Galaxy omnibus (which I did at first) may be slightly perplexed by it. This is due to the removal of a few words at the end. At the end of the original version it is very blatantly suggested that the escaped insane "Designer Person" is actually President Ronald Reagan. In the original, which ended up being omitted in many later editions, the thing was actually called a "Reagan." "A kindly looking man with lots of pleasant laugh lines around his face" and "seemed to be babbling gently to himself" and who was "totally benign, which is what makes him so dangerous" and there is "nothing he will not do if allowed, and there is nothing he will not be allowed to do."
It's obvious that Adams only wrote this short story to express his political views. Reread it with Ronald Reagan in mind and it's actually quite funny.